There are two types of sharp-force injuries: incised and stabbed. The incised wound is longer than it is deep. The stab wound is defined as a puncture wound that is deeper than it is wide (Figs. 19.19, 19.20, 19.21). The wound margins of sharp-force injuries are clean and lack the abraded edges of lacerations from blunt forces. Forensic information can be gathered during the examination of a stab wound. Some characteristics of a knife blade, single- or double-edged, can be determined by visual inspection. Characteristics such as serrated versus sharp can be determined if the blade was drawn across the skin during insertion or withdraw from the victim. Serrated blades do not always leave these characteristic marks.
Stab Wound. A stab wound from a single-edged knife blade will impart a sharp edge and a dull edge to the wound. If the blade penetrates to the proximal portion of the blade, a contusion may result from contact with the hilt of the knife.
Single-Edge Stab Wound with Hilt Mark. A single-edged stab wound with a small hilt mark associated with the dull edge of the blade. (Photo contributor: William S. Smock, MD.)
Single-Edge Stab Wound. A stab wound from a single-edged knife blade. The superior portion of the wound corresponds with the dull edge of the blade and the inferior with the sharp edge of the blade. (Photo contributor: William S. Smock, MD.)
When a patient presents with superficial and/or parallel incisions, the wounds must be considered intentionally self-inflicted until proven otherwise (Figs. 19.22 and 19.23). The emergency physician should obtain a more detailed history, including the number of “swipes” the alleged assailant made with the knife. Accidental, self-inflicted incised wounds on the palm or palmar aspect of the fingers are common on the hands of suspects in violent stabbings (Fig. 19.24). The suspect’s hand slips down the handle and makes contact with the knife blade when the blade impacts a firm object, like bone (Fig. 19.25).
Self-Inflicted Incised Wounds. Superficial and/or parallel incisions are pathognomonic for intentional self-inflicted wounds. This patient has acute and healed self-inflicted incisions in the same location on the anterior lateral aspect of her neck. (Photo contributor: William S. Smock, MD.)
Self-Inflicted Incised Wounds. Examination of the “victim’s” chest reveals multiple superficial incisions. The patient initially claimed she was “assaulted” but later admitted that the wounds were self-inflicted. (Photo contributor: William S. Smock, MD.)